Yes, you are entitled to avoid non-kosher contamination in your food. But whether an airline needs to facilitate that is a separate question. I doubt they have any obligation to provide dietary choices to passengers (they are not obliged to provide food at all, so how could they be obliged to meet specific requirements), but they do so as a business decision. In doing so they do their best to meet those requirements. While they may have a legal obligation to ensure there are no nuts in a meal provided do someone with an allergy, I doubt they could be required to meet all the tests for religious observance. By all means ensure no prohibited foods (pork, shellfish) but expecting that they meet all the minutiae of kosher or halal is not reasonable. (Although halal slaughter is an easy standard to pass.)
I seem to recall that in Islam, the obligation to accept hospitality is higher than the obligation to adhere to dietary rules. That could provide a useful way to consider airline food. Choose the option that most closely meets key observance criteria, don't insist on detailed adherence to some set of rules.